1. Field of the Invention
The present invention relates to an audio information processing system suitable for devices such as the optical disc player, the mobile telephone, etc., that can deal with digital audio information.
2. Related Art
Conventionally, the optical disc player adapted to the so-called DVD(Digital Versatile Disc) format (referred to as a xe2x80x9cDVD playerxe2x80x9d hereinafter) can play back not only the audio and the moving picture from the optical disc adapted to the DVD format but also the audio adapted to the CD(Compact Disc) format.
As shown in FIG. 1, for example, such DVD player system comprises a decoder 102 for decoding a digital signal read from an optical disc 101, and a D/A converter 103 for converting the digital signal decoded by the decoder 102 into an analog signal.
The digital signal to be input into the D/A converter 103 is different depending upon which format the optical disc 101 is adapted to the DVD formator the CD format. For example, if the digital audio information formatted by the CD format is supplied, the digital audio information whose sampling frequency of 44.1 kHz is supplied with 16-bit precision. In contrast, if the digital audio information formatted by the DVD format is supplied, the digital audio information which has higher tone quality than that formatted by the CD format and whose sampling frequency of 192 kHz (96 kHz) is supplied with 24-bit precision. For this reason, it is the existing circumstances that the D/A converter 103 has a complicated configuration rather than the normal case to play back the digital audio information formatted by different formats.
However, in the conventional DVD player system, the D/A converter 103 is constructed to conform with both formats such that the digital audio information formatted by both formats can be played back. In this case, in playing back the digital audio information formatted by the CD format, the digital audio information whose sampling frequency is 44.1 kHz is played back with 16-bit precision as it is. Therefore, there is such a problem that, although the D/A converter 103 has a high-level function to play back the digital audio information formatted by the DVD format, it merely plays back the digital audio information with low tone-quality. This problem becomes remarkable when the bit number and the sampling frequency of the original digital audio information are lowered.
The present invention has been made in view of the above drawbacks, and it is an object of the present invention to provide an audio information processing system capable of playing back digital audio information with high tone quality without complicating a configuration of a D/A converter.
In order to achieve the above object, there is provided an audio information processing system comprising: bit-number extending means for extending a bit number of supplied digital audio information; and digital audio information output terminal for outputting the digital audio information extended by the bit-number extending means.
According to the present invention, since the digital audio information whose bit number is extended by the bit-number extending means is output via the digital audio information output terminal, the audio information whose tone quality is improved by extending the bit number can be output digitally.
In the preferred embodiment of the present invention, the bit-number extending means extends the bit number into a predetermined bit number irrespective of the bit number of the supplied digital audio information.
Also, in order to achieve the above object, there is provided an audio information processing system comprising: resampling means for resampling supplied digital audio information at a sampling frequency higher than an original sampling frequency; and digital audio information output terminal for outputting the digital audio information which is subjected to resampling process by the resampling means.
According to the present invention, since the digital audio information which is resampled by the resampling means at the sampling frequency higher than the original sampling frequency is output via the digital audio information output terminal, the audio information whose tone quality is improved by the resampling process can be output digitally.
In the preferred embodiment of the present invention, the resampling means performs the resampling process at a predetermined sampling frequency irrespective of the sampling frequency of the supplied digital audio information.
Also, in order to achieve the above object, there is provided an audio information processing system comprising: bandwidth extending means for extending a frequency band of supplied digital audio information; and digital audio information output terminal for outputting the digital audio information which is extended by the bandwidth extending means.
According to the present invention, since the digital audio information whose frequency band is extended by the bandwidth extending means is output via the digital audio information output terminal, the audio information whose tone quality is improved by extending the frequency band can be output digitally.
Also, in order to achieve the above object, there is provided an audio information processing system comprising: bit-number extending means for extending a bit number of supplied digital audio information; resampling means for resampling the digital audio information, whose bit number is extended by the bit-number extending means, at a sampling frequency higher than an original sampling frequency; bandwidth extending means for extending a frequency band of the digital audio information which is subjected to resampling process by the resampling means; and digital audio information output terminal for outputting the digital audio information from bandwidth extending means.
According to the present invention, since the digital audio information whose bit number is extended by the bit-number extending means, which is resampled by the resampling means at the sampling frequency higher than the original sampling frequency, and whose frequency band is extended by the bandwidth extending means is output via the digital audio information output terminal, the audio information whose tone quality is improved by the bit expansion process, the resampling process, and the bandwidth extending process can be output digitally.
In the preferred embodiment of the present invention, the bit-number extending means extends the bit number into a predetermined bit number irrespective of the bit number of the supplied digital audio information, and the resampling means performs the resampling process at a predetermined sampling frequency irrespective of the sampling frequency of the supplied digital audio information.
In the preferred embodiment of the present invention, the audio information processing system further comprises controlling means for controlling the bit-number extending means, the resampling means, and the bandwidth extending means based on bit number information and sampling frequency information of the supplied digital audio information so as to execute any one of or any combination of a bit number extending process, a resampling process, and a frequency band extending process.
According to the preferred embodiment, the optimum process which is suitable for the bit number information and the sampling frequency of the supplied digital audio information can be performed by combining arbitrarily the bit number extending process, the resampling process, and the frequency band extending process.
Also, in order to achieve the above object, there is provided an audio information processing system comprising: bit-number extending means for extending a bit number of supplied digital audio information; and digital/analog converting means for converting the digital audio information from the bit-number extending means into analog information according to the bit number of the digital audio information which is extended by the bit-number extending means.
According to the present invention, since the digital audio information from the bit-number extending means is converted in the analog information by the digital/analog converting means according to the bit number of the audio information which is extended by the bit-number extending means and is output, the digital audio information can be played back in high tone quality.
In the preferred embodiment of the present invention; the bit-number extending means extends the bit number into a predetermined bit number irrespective of the bit number of the supplied digital audio information.
According to the preferred embodiment, the digital/analog converting means can be operated constantly irrespective of the supplied digital audio information, and thus the digital audio information can be reproduced in high tone quality without complicating a configuration of the digital/analog converting means.
Also, in order to achieve the above object, there is provided an audio information processing system comprising: resampling means for resampling supplied digital audio information at a sampling frequency higher than an original sampling frequency; and digital/analog converting means for converting the digital audio information from the resampling means into analog information according to the sampling frequency used in resampling process by the resampling means.
According to the present invention, since the digital audio information from the resampling means can be converted into the analog information by the digital/analog converting means according to the sampling frequency used in the resampling process by the resampling means, the digital audio information can be reproduced in high tone quality.
In the preferred embodiment of the present invention, the resampling means performs the resampling process at a predetermined sampling frequency irrespective of the sampling frequency of the supplied digital audio information.
According to the preferred embodiment, the digital/analog converting means can be operated constantly irrespective of the supplied digital audio information, and thus the digital audio information can be reproduced in high tone quality without complicating the configuration of the digital/analog converting means.
Also, in order to achieve the above object, there is provided an audio information processing system comprising: bandwidth extending means for extending a frequency band of supplied digital audio information; and digital/analog converting means for converting the digital audio information from the bandwidth extending means into analog information according to the frequency band of the digital audio information which is extended by the bandwidth extending means.
According to the present invention, since the digital audio information from the bandwidth extending means can be converted into the analog information by the digital/analog converting means according to the frequency band used of the audio information which is extended by the bandwidth extending means, the digital audio information can be reproduced in high tone quality.
Also, in order to achieve the above object, there is provided an audio information processing system comprising: bit-number extending means for extending a bit number of supplied digital audio information; resampling means for resampling the digital audio information, whose bit number is extended by the bit-number extending means, at a sampling frequency higher than an original sampling frequency; bandwidth extending means for extending a frequency band of the digital audio information which is subjected to resampling process by the resampling means; and digital/analog converting means for converting the digital audio information from the bandwidth extending means into analog information.
According to the present invention, since the digital audio information whose bit number is extended by the bit-number extending means, which is resampled by the resampling means at the sampling frequency higher than the original sampling frequency, and whose frequency band is extended by the bandwidth extending means is converted into the analog information by the digital/analog converting means to output, the digital audio information can be reproduced in high tone quality.
In the preferred embodiment of the present invention, the bit-number extending means extends the bit number into a predetermined bit number irrespective of the bit number of the supplied digital audio information, and the resampling means performs the resampling process at a predetermined sampling frequency irrespective of the sampling frequency of the supplied digital audio information.
According to the preferred embodiment, the digital/analog converting means can be operated constantly irrespective of the supplied digital audio information, and thus the digital audio information can be reproduced in high tone quality without complicating the configuration of the digital/analog converting means.
In the preferred embodiment of the present invention, the audio information processing system further comprises controlling means for controlling the bit-number extending means, the resampling means, and the frequency band extending means based on bit number information and sampling frequency information of the supplied digital audio information so as to execute any one of or any combination of a bit number extending process, a resampling process, and a frequency band extending process.
According to the preferred embodiment, the optimum process which is suitable for the bit number information and the sampling frequency of the supplied digital audio information can be performed by combining arbitrarily the bit number extending process, the resampling process, and the frequency band extending process.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.